The Glock 31 is another addition to the Glock family line of successful semi-automatic pistols for military, security and civilian applications. It is based on the Glock 22 model series, a full-size .40 S&W version of the original Glock 17 9x19mm Parabellum model. Of particular note in these mentioned firearms was the use of high magazine capacities - 15- to 17-round counts. With the growing use of the .357 SIG cartridge, Glock developed the Glock 31 model specifically to fire this round with alterations made to the barrel, magazine, slide and receiver to compensate for increased recoil.
Outwardly, the Glock 31 follows the tried-and-true lines of the Glock family series as a whole. The series features skilful use of plastics and metal in a compact form. The appearance is dominated by the slide which features ribbing at the rear to provide for a firm grip when managing said slide. The grip is ergonomically formed with finger grooves for a firm hand hold while the curved trigger unit sits within an oblong trigger guard. All controls (slide release, magazine release, safety) are within easy reach of the firing hand's thumb. The magazine is inserted into the base of the pistol grip in a conventional manner. With the safety removed, the slide can be actuated to introduce a cartridge into the chamber. A recoil spring is set under the barrel, both being shrouded by the slide, and controls the recoil action. The action is categorized as short recoil with a tilting barrel design.
The Glock 31 is chambered for the .357 SIG cartridge and holds up to 15 in a standard capacity magazine. A 17-round count is also available which no doubt protrudes from the base of the grip some. The weapon measures a running length of 186mm (7.32 inches) with a 138mm (5.43 inch) height. Overall weight is 660 grams when unloaded and 940 grams when loaded with a full magazine. Trigger pull is 5.5lbs of pressure. The barrel sports a right-hand hexagonal rifling pattern. Iron sights are provided at the rear and front of the slide.
The Glock 31 has proven particularly popular with police forces for its lightweight handling and high-magazine capacity.